The present invention relates to polymeric fluorinated dioxole and medical devices comprising the same. In particular, the present invention relates to ophthalmic devices comprising polymeric fluorinated dioxole.
Advances in chemistry of materials for medical devices, such as ophthalmic lenses, have increased their compatibility with a body environment and the comfort for their extended use therein. The extended use of contact lenses requires that materials for these lenses allow sufficient rates of transport of oxygen to the cornea to preserve its health because the cornea does not have blood vessels for the supply of oxygen and must receive this gas by its diffusion through the epithelial layer on the outer surface of the cornea.
While there exist rigid gas permeable (“RGP”) contact lenses, which have high oxygen permeability and which move on the eye, RGP lenses are typically quite uncomfortable for the wearer. Thus, soft contact lenses are preferred by many wearers because of comfort. (Soft materials are those exhibiting low modulus of elasticity, such as less than about 150 g/mm2.) Moreover, a contact lens which may be continuously worn for a period of a day or more (including wear during periods of sleeping) requires comfort levels that exclude RGP lenses as popular extended-wear candidates. Among the soft contact lens materials having high oxygen permeability have been polymers containing siloxane groups. For example, see U.S. Pat. Nos. 3,228,741; 3,341,490; 3,996,187; and 3,996,189.
Contact lens materials having oxygen permeability up to 60 barrers have been made with combinations of fluorinated alkyl methacrylates and polysiloxane macromers. For example, U.S. Pat. No. 4,486,577 discloses an RGP lens formulation comprising hexafluoroisopropyl methacrylate and poly(dimethylsiloxane) macromer. Another combination is taught in U.S. Pat. Nos. 4,540,761 and 5,023,305, which disclose the addition of trifluoroethyl methacrylate to an RGP-type formulation containing oligosiloxanylalkyl methacrylate.
However, attempts to increase the oxygen permeability by increasing the proportions of siloxane-containing polymers and fluorinated monomers conflict with the need to keep other physical properties, such as hardness and dimensional stability and toughness, at a useful level.
Therefore, there is a continued need to provide materials having improved oxygen permeability but avoiding the limitations of the prior-art materials. In particular, it is very desirable to provide materials for ophthalmic devices, which materials have improved oxygen permeability and physical strength, and at the same time provide comfort to the users.